My C6 is a refinement of my C5, and the Z51 package provides better brakes, shorter gear ratios, and a tight suspension. I replaced the Lexus- sounding exhaust with a Corsa Sport system, and now it sounds like a Corvette. The bad news is little irritating problems, like a plethora of interior rattles, and a chronic roof panel rattle. Fixed under recall, it still makes noise. The worst problem is known as "dead battery syndrome" due to the need to shut off the car in reverse, or it stays in accessory and it kills your battery. This ruined a weekend for me. The F1 Supercar Run Flats are very good for run flats, and I can accept the low 220 wear rating in trade for great handling.
Head up display, XM radio, Z51 package.
Shorter throws in 6 speed, no shut-off in reverse, more reliable electronics without all the glitches, no more rattles.